Should be no strain. With plugs out ,crank will rotate easy. With rockers off ,cam just riding in the bearings....no spring pressure, no chance of valve interference with pistons. Crank could go slightly CCW, a few degrees , could just be the pic. Cam rotates to line up with crank when piston is at it's highest point in the cylinder. For your application. Crank gear timing mark should be exactly at 12:00. With chain off, bolt your timing gear on and align marks crank@12;00,cam@6:00. Unbolt cam gear ,should only have been finger tight. Assemble chain per instructions. Be patient ,may take a few tries for proper alignment. Kolektor is correct. Even with cam bolts installed. Final assembly, bolts should receive a little Permatex blue locktite.
Now would also be a good time to check your pushrods---one at a time as used valve train MUST be kept in order as disassembled.
I would do initial valve adjustment prior to installation of distributor, with timing cover off. Check for valve closure and piston interference. Should be ok, none the less we check anyway.
With valves adjusted (plenty in the forums on this ,cold setting) Rotate your engine back to crank@12:00 , cam@12:00 ,#1 piston will be at TDC...install your distributor. Rotor to #1 tower position. Lock it down for now.
Button the rest of this project up. Cold set the timing, check for potential vacuum leaks. Set, than 1.5 turns out on you mixture screws. Fire it up, check timing. Run through the valves again, fine tune the carb.
